Inbound mosaic of Mercury

. During its three encounters with Mercury in 1974-75, the Mariner 10 spacecraft obtained thousands of images of the same sunlit hemisphere of the planet. Individual frames acquired by the approaching spacecraft have been joined together in this mosaic. The tiny, brightly rayed crater (just below center top) was the first recognizable feature on the planet's surface and was named in memory of astronomer Gerard Kuiper (1905-1973), a Mariner 10 team member. From this perspective, Mercury looks similar to the Moon, with a heavily cratered surface, but close-up inspection of individual surface features reveals some fundamental differences. (Courtesy of JPL and NASA.)